Systemic sclerosis (SSc) or scleroderma is an autoimmune connective tissue disease of unknown etiology. Twins provide a unique opportunity to assess the role of inherited vs. acquired genetic/environmental factors in disease development and provide the ideal controls for examining changes in gene expression at the tissue level. The aims of the proposed study are: (1) examination of a cohort of twins with SSc to determine concordance for disease; (2) confirmed pairs of twins with SSc (monozygotic and dizygotic, concordant and discordant) will be further analyzed by a detailed physical and laboratory examination (including cytogenetic analysis on peripheral blood and dermal fibroblasts, analysis of differential gene expression in dermal fibroblasts).